Measurement of Time Response of Laser-Triggered GaAs Photocathode

An RF gun with a laser-triggered photocathode is a very attractive as an injector for linear accelerators since it can produce a low-emittance high-current electron beam with originally short pulse length. A GaAs photocathode can generate a polarized electron beam. The time response of GaAs photocathode is very important for RF gun operation if it is comparable with RF period. An experirnental facility has been fabricated to measure the length of electron bunch extracted from GaAs photocathode illuminated by laser pulse of 98 ps (FWHM). The method of hunch length measurement using circular scanning in RF cavity was developed. We use 50 kV DC gun for beam extraction. The minimum measured bunch duration was 106 +/- 20 ps (FWHM) for 4.5. 10^8 electrons per pulse. In this report we describe the experimental setup and obtained results